McCartney's spokesman was noncommital in an email to TheWrap: "Neither confirming nor denying, sorry. Everyone will have to wait and see," he said.

It wouldn't be the craziest thing that's ever happened: McCartney played with Grohl and others at the end of this year's Grammy Awards (pictured).

The Sun said guitarist Pat Smear, who played with Nirvana in the months before Kurt Cobain's 1994 suicide, would also perform Wednesday, Grohl, Novoselic and Smear have not performed together since Cobain's death.

The Sun said McCartney recently jammed with Grohl, Novoselic and Smear after Grohl invted him to "jam with some mates."

We're pretty sure Grohl didn't say mates.

McCartney, 70, was quoted in the Sun saying he suggested they "just make something up."

"I didn’t really know who they were. They are saying how good it is to be back together. I said ‘Whoa? You guys haven’t played together for all that time?'" the Sun quoted the ex-Beatle as saying. “And somebody whispered to me, ‘That’s Nirvana. You’re Kurt.’ I couldn’t believe it.”

The Rolling Stones, Jon Bon Jovi, Eric Clapton, Billy Joel, Bruce Springsteen and the E Street Band, Alicia Keys, Eddie Vedder and Kanye West are set to play at the benefit concert.

It will air at 7:30 p.m. ET on HBO, AMC. VH1 and numerous other channels. Viewing information is here.